This application claims the priority of German Patent Application Serial No. 299 23 059.7, filed Nov. 11, 1999, the subject matter of which is incorporated herein by reference.
The present invention relates in general to an electromotive adjustment assembly.
A conventional electromotive adjustment assembly is known which has two aligned spindles disposed in a common housing. Each spindle is driven by a motor via a reduction gear unit, so that operation of the spindles can be effected independently from one another in both rotation directions. Spindle nuts mounted on the spindles interact with articulated levers which ultimately convert a linear movement of the spindle nuts in a rotation movement of the furniture item being adjusted, or vice versa, so as to move the furniture item, for example, the head board or foot boards of a slatted frame, into the desired position. This type of adjustment assembly is, however, not suitable when the height of large-area components, such as tabletops, is intended to be moved.
It is thus an object of the present invention to provide an improved electromotive adjustment assembly, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved electromotive adjustment assembly which is universally applicable for realizing a height adjustment of a structure, such as a furniture item, and yet is simple in construction.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing a motor unit positioned between the spindles and coupled in driving relationship with the spindles for rotating the spindles, with the spindles being secured against displacement longitudinally in the direction of the axis, and by providing a lifting device including profiled lifting members mounted at an angle to a structure to be lifted, and flexible pull strands linked to the spindle nuts and trained over deflection rollers for attachment of their free ends to the lifting members.
It is now possible to mount an electromotive adjustment assembly according to the present invention, for example, underneath a table top with the spindles oriented horizontally, because, in accordance with the present invention, horizontal movements are converted into vertical movement. The profiled lifting members can be elevated via the pull strands as the spindle nuts move toward one another, whereas a lowering of the structure is implemented by reversing the rotation direction of the spindles, thereby also preventing the possibility of a sudden drop of the structure. The arrangement of the pull strands depends on the application at hand.
According to another feature of the present invention, the two spindles are oriented in alignment to one another and have pitches in opposite direction. In this manner, the motor unit for the spindles is especially simple in nature as a small number of drive wheels is only required. The opposing pitches of the spindles ensure a travel of the respectively attached spindle nuts in opposite directions. Since right-hand spindles are generally preferred, it is also proposed that the spindles rotate in opposite directions. This can be realized through appropriate configuration of the motor unit for driving the spindles. As the output speed of an electric motor is high, it is suitable to couple the motor unit with a reduction gear unit, preferably a worm gearing, for transmitting the power of the motor unit to the spindles.
In order to prevent the flexible pull strands from touching the spindles, lifting or thrust tubes are mounted onto the spindle nuts to follow the movement of the spindle nuts, whereby the elastic pull strands are attached to the free ends of the lifting or thrust tubes. Such a configuration is suitable, for example, for a table with two lateral columns.
According to another feature of the present invention, the profiled lifting members are inner profiled sections which are guided in outer guide tubes. The inner profiled sections may be pipes and may be made, for example, of aluminum. In the case of a table, the guide tubes may be formed by the table legs, with the inner profiled sections mounted to the underside of the tabletop at a right angle thereto. The deflection rollers are suitably arranged on confronting areas in the upper zone of the guide tubes.
In order to keep friction during travel of the inner profiled sections to a minimum and to prevent a tilting or canting of the inner profiled sections, the inner surfaces of the outer guide tubes have inner surfaces positioned at a distance to the outer surfaces of the inner profiled sections, whereby slide pieces may be provided which can be mounted to the inner surfaces of the outer guide tubes and/or the outer surfaces of the inner profiled sections. Thus, the inner profiled sections can be guided in the guide tubes in an enclosed environment.
When utilizing an electromotive adjustment assembly for height adjustment of a tabletop, it may be required to move four inner profiled sections. In order to be able to use only a single adjustment assembly according to the present invention, it is proposed to use rods which are secured to the lifting tubes transversely thereto, for attachment of the flexible pull strands. The electromotive adjustment assembly according to the present invention is then disposed in the middle between opposing guide tubes. As only a single adjustment assembly is used, there is no need for a separate synchronizing control unit.
Operation of the electromotive adjustment assembly may be realized, for example, by a hand switch or, wireless, via a remote control.
Depending on its size, the structure to be moved may be relatively heavy. On the other hand, the power output of the motor unit should be as small as possible. In order to adjust a relatively heavy structure while still using a small motor unit, it is proposed to configure the pull strands as parts of a block and tackle. The power output of the electromotive adjustment assembly may then be kept to a minimum depending on the number of rollers.
According to another feature of the present invention, the spindles or spindle nuts may be associated to a gas spring, regardless of the configuration of the flexible pull strands, for assisting the lifting movement. Gas springs accommodate a piston rod which can move in and out, whereby a retraction of the piston rod or rods is realized by the own weight of the structure to be lowered.
The electromotive adjustment assembly according to the present invention is simple in construction and thus cost-efficient, and yet is capable to move even structures that are relatively heavy.